Protective device.



No. 807,963. PATENTED DB0. 19, 1905 G. W. PIGKARD.

PRO'IEGIIVE)DEVICE.l APPLIGATION FILED DEG. 21, 1904` 2?* LINE 2] 3% To swn'cH BoARu www W 7k 'UNITED rwATENT onirica,

GREENLEAF VVHITTIER IICKARD, OF AMESBURY, MASSACHUSETTS, AS-

SIGNOR TO AMERICAN TELEPHONE AND TELEGRAIH COMPANY, A

CORPORATION OF NEW YORK.

PFroTEoTivE` DEVICE.

Specification of Letters Patent.

Patented Dee. 19, i905.

Original application iiled April 14, 1904, Serial No. 203,159. Divided and this application iiled December Z1, 15104. Serial No. 237,851.

To a/ZZ whom it may concern:

Be it known that I, GREENLEAF WHITTIER PICKARD, residing at Amesbury, in the county of Essex and State of Massachusetts, have invented certain Improvements in Protective Devices, of which the following is a speciiication.

The standard protectors used for the protection of central-oillce'and substation telephone apparatus comprise open-space cutouts by way of which trespassing high-pressure currents are diverted from the protected apparatus and passed to earth. lightning discharges or momentary crosses with high-pressure circuits, such as electriclight or power circuits, the high-pressure current or charge passes to earth bya disruptive discharge across the open space or air-gap, while in case of continued crosses the cut-out establishes acontinuous short-circuit across the air-gap to ground. rlhe resistance offered by the open space prevents the passage to ground of the relatively low-pressure telephone talkingand ringing currents.

The open-space arresters or protectors now generally used consist of. two carbon terminal blocks or electrodes separated by a mica-plate or sheet, against the opposite faces of which the blocks bear, one terminal block being connected to one ofthe telephone-line conductors and the other to ground. The mica plate is cut away or left open at its middle, thereby frming a narrow open spaceor air-gap between the adjacent faces of' the terminal .blocks Said adjacent faces are roughened,

` and at least onefof them is provided with an inserted .globule of fusible metal, which is rubbed down liush with the surface of the block. In case of continued arcing across the -it has one serious disadvantage.

open space the globulel fuses and bridges the open space, thereby establishing a Apermanent short-circuit to ground. While the cut-out above described eiliciently serves its purpose, 'lhe rough carbon surfaces are disintegrated by arcing or spark discharges between the carbons and to a lesser degree .by mechanical vibration. The i fine carbon particles thus loosened deposit acrossthe open space or air-gap ,separating the blocks, thereby establishing a permanent ground or a path by which the norline may leak to earth. 4Vephonic current 1s conmal current of th In case ofV sequently interfered with, and the deposits have to be periodically removed to maintain the conditions necessary for efhcient operation. Frequent visits by employees for rcmoving these deposits, and -thereby clearing the lines from grounds at cable-terminals, substations, central oilces, and other points upon the lineswhere these protectors are used, involve heavy maintenance expense. Other materials, such a` aluminium, tried in place of the carbon blodks have'not proved equal in efiiciency to the latter.- It is therefore desire able to improve` the carbon blocks in such manner as to avoid the diiiculties and expense referred to above. This object I accomplish by impregnating the porous carbon blocks with a suitable binding material or agent which binds the fine particles thereof together and prevent-s disintegration by arcing or mechanical vibration without in other respects detrac'ting from the efficiency of the carbon blocks.

According' to the preferred method oftreatment the carbon blocks are immersed 'for thirty minutes in a solution of one and fourtenths pounds of rosin in one gallon of turpentine. During the immersion thesolution is maintained at a temperature of from 15()O to io Fahrenheit to render it highly iiuid and enable the porous blocks to readily absorb the same. The'blocks are then removed from the solution, drained of the liquid, and thoroughly dried in air at a temperature of from 150O to 160O Fahrenheit for twenty-four hours, thereby evaporating the turbentine and leaving the rosin as the binding material. After the' drying thefaces of the blocks are ground in the usual way to remove the film or covering of rosin and lto present a rough carbon surface. The blocks are finally washed in water to'remove fine carbon particles from the surface thereof and then dried.

This application is a division of my appli- Canon', tied April i4., 190i, serial No. 203,159, wherein I. have claimed'the improved block, terminal, or electrode and the process of making the same.

The invention of the present application resides in the electrical protective device `formed in part of one or more of said blocks, terminals, or electrodes.

In the accompanying drawings, Figure i tection outfit of the type employed in telephone equipments. 1Fig. 2 is a perspective view of two carbon blocks and their separating mica plate.

Referring to the drawings, 3 is a metal or Yother cond uctinesu pport, to which four springb l:

blades 5, 6, 7, and 8 are secured by a bolt 9. The .blades are insulated fromeach other and from the support by interposed blocks of insulation.

10 and 11 are heatingcoil appliances of welllrnown construction adapted to open the cirvuit upon the continued passage thereover of current of excessive strength. The protective device 10 is held between blades 5 and 6 and the device 11 between blades 7 and 8. 12 is a double bracket or plate secured to the upper end of the grounded conducting-supporti? and projecting vertically beyond the same.

Two carbon blocks 13 and 14, impregnated with a binding material in themanner described and separated by 'an insulating sheet or plate of mica 15, are tightly clamped Logether between the bracket 12 and the upper end of spring-blade 5, said blade lying in a groove 16 in block le. rllhe mica plate 15 has an opening in its middle, thereby providing between the adjacent rough surfaces of the carbon blocks an open space or air-gap. A globule 17, of a suitable fusible alloy, is inserted in a recess in the inner face of block I3 and rubbed down 'flush with said face in substantial accord with the patent of A. C. White, No. 438,788, @ctober 21, 1890. Carbon blocks 18 and 19, similarly arranged, are clamped betweenthe bracket l2 and the upper end of spring-blade 7. l

Assuming the protective appliance tov be employed 'for the protection of' switchboard apparatus, the circuit connections are as i'ollows; @ne line conductor 20 is connected with the bolt 9, which holds the several springblades in place, and the circuit continuesfrom said bolt to spring-blade` 7, thence through the heating-coil device 11 and spring-blade 8 l and Wire 23 to the switchboard apparatus, re-

turning by conductor 21 to spring-blade5, and thence by heatingoil; device 10 and spring-blade 6 to the complementary line conductor 22.. rllhe bar 8, to which the metallic bracket 12 is attached, is grounded at G by a conductor 2i. A higl'i-pressure current or discharge, such that of a stroke of lightsoeces ning or a discharge accruing from a cross with a high-voltage light or power-circuit conductor` coming in, for example, over conductor 20, will pass by bolt 9 to spring-blade 7, to carbon block 19, and from the latter will disruptively discharge across the open space to carbon block 18, passing from the latter to ground by way of bracket 12 and conductor 24. ln case this discharge should be followed by a persisting arc the globule 17will be fused,

thereby bridging the space between blocks 19 and 18 and establishing a permanent short circuit to ground.

With carbon blocks heretofore commonly used it has been necessary to periodically remove from the open space between the blocks deposits of iine carbon particlesor dust loosened from the carbon blocks by arcing of the current or by mechanical vibration, as already described. It has been found'that such deposits are avoided by using the herein-described carbon blocks impregnated with a binding material.

Vif hat is claimed is- 1.1m an electrical protective device, two terminals or electrodes separated by a narrow open space, one of said terminals consisting of a block of porous conducting material impregnated with a binding material.

2. In an electrical protective device, two terminals or electrodes separated by a narrow open space, one of said terminals consisting of a porous carbon block impregnated with a binding material.

3. in an electrical protective device, two terminals or electrodes separated by a narrow open space, said terminals consisting of porous carbon blocks impregnated with a binding material. ,Y 4f. In an electrical protective device, two terminals or electrodes separated by a narrow open space, said terminals consisting of porous carbon blocks impregnated with a binding material, the adjacent faces of said blocks being exposed carbon surfaces.

In testimony whereof I have signed my name to this specification, in dig-,presence of two subscribirig witnesses, this 19th day of December. 1904.

GREENLEF WHITTIER, PICKARD.

Witnesses:

Gino. WILLIS Pinnen, JOSEPH A. GATELY.

IOO 

